The present invention relates to a pressure-gas operated dispensing means for fluids comprising a first container connectible via a first gas line to a pressure gas source, and whose outlet is connected to a discharge line, and a second container also connectible to the pressure gas source via a second gas line and a first valve, which second container is connected by a fluid line to a fluid source.
It has been known, for expelling fluid from a container, e.g. for spraying fluid on a material to be treated, to use dosing pumps adapted to produce the pressure required to expel the fluid. In case of dosing pumps in the form of piston pumps, shocks and vibrations may occur so that dosing is not performed uniformly but by impact blows. If spindle pumps are used for dosing, high-frequency and stochastic vibrations are caused, thus again affecting a continuous uniform dispensing of fluid for the purpose of atomization. A continuous atomization is, for example, required for spraying flavoring agents on tobacco or for spraying fluid on textiles, etc.
It has also been known to dispense pressurized fluids from a vessel. Due to the timely and constant pressure, fluid may be dispensed uniformly, however, for refilling fluid, the pressure vessel must be loaded periodically. During the loading operation, no fluid may be dispensed. With such a batchwise filling of fluid into the pressure vessel, care must be taken that the pressure vessel contains the exact amount of fluid required. Otherwise, dispensing must be interrupted prematurely, or, alternatively upon the supply of the determined amount of fluid, a residual quantity of fluid still present in the vessel must be removed. Moreover, due to the high pressures, the use of pressure vessels are governed by strict safety requirements and form a constant source of risk.
A known dispensing means of the above mentioned type, shown in U.S. Pat. No. 1,460,389, comprises two containers, one being connected to an expansion tank and the other to a pressure tank. If one container is filled with fluid, the escaping gas expelled from said container gets into the expansion tank. The pressure tank supplies pressure gas to the other container to expel the fluid therefrom. By this means, one container may be filled while the other is emptied and vice versa. In addition to the pressure tank, the known assembly calls for an expansion tank and a compressor which removes gas from the expansion tank to condense the gas to be supplied to the pressure tank. Each of the two containers is to be connected to at least three lines. Furthermore, a high expenditure is necessary because of the number of valves required.
Accordingly, it is the object of the present invention to provide a dispensing means as described above which requires only a simple pressure gas source, e.g., the usually existing compressed air line, and which may be realized with simple devices and reduced technical expenditure.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The problem of the present invention is solved in that by a second valve, the fluid line is connected to the discharge line as well as to the first container, the second gas line being connectible to a vent line if the second gas line is separated by said first valve from the pressure gas source.
According to the present invention, the second container is a reserve tank from which fluid is pressed into the first container or into the fluid line extending out of the first container if the latter is nearly empty. During the fluid transfer from the second container into the first container, both containers connected to the pressure gas source are under equal pressure action. Thus, pressure fluctuations in the fluid line extending out of the first container are avoided. Hence, fluid is filled from the second container to the first container during the dispensing operation which need not be interrupted or changed. If the first container is filled from the second container, the second container is refilled again. To this effect, the gas line of the second container is connected to the vent line, with the fluid path from the second container to the first container being locked. Refilling of the second container may be now realized from the external fluid source until it is filled, while fluid is being continuously pressed out of the first container. In a way, the two containers form a tandem arrangement in which the first container is emptied while the second is being filled, whereas the first container is filled when the second is emptied. Preferably, the volume of both containers is approximately equal. The containers may be relatively small so that only low residual amounts of fluids are left in them when the dispensing device is disconnected. Due to the constant decanting of the containers, small container volumes are sufficient.
The pressure gas source may be the compressed air supply usually available in factories which delivers compressed air at a pressure of about 6 bar.
For decanting fluid from the second container to the first, the pressure in the second container should be somewhat higher than that in the first container. Said pressure difference may be produced in that in the gas line extending from the gas pressure source to the first container, a throttle point is provided which does not exist in the line extending to the second container.
The pressure difference required for decanting may be easily caused by mounting the second container at a level higher than the first container and by underconnecting the gas lines of both containers if the fluid line of the second container is connected to the discharge line. During the decanting phase, both containers are connected to the same gas pressure. The required pressure difference is caused by the height difference between the containers. The bottom wall of the second container is situated at a higher level than the upper wall of the first container. No additional external source for producing the pressure difference in the refilling phase is required.
On embodiment of the invention will be explained hereinafter with reference to the drawings.